Definition Questions Flashcards
3 Unique features of Stem Cells
1) Stem cells can remain undifferentiated & unspecialised for a long time
2) Stem cells are capable of dividing indefinitely & self- renewal by mitosis
3) Stem cells can undergo differentiation, giving rise to specialised cell types upon receiving appropriate signals
Meaning of totipotency + example
Totipotent stem cell means they can differentiate to form all cell types that make up an entire organism including the extra-embryonic tissue e.g placenta
Zygotic Stem Cell
Meaning of Pluripotency + example
Pluripotent stem cells means that they can differentiate to form any cells types that make up an organism, excluding the extra-embryonic tissue e.g placenta
Embryonic Stem cell
Meaning of Multipotency + example
Multipotent stem cells can differentiate into a limited and related range of cell types and tissues in an organism.
Blood stem cells
What are the 7 ethical implication of the application of stem cells in research and medical applications?
1) Destruction of embryos to obtain embryonic stem cells poses as a moral dilemma of destroying a potential human life to save another human life.
2) Controversial creation of embryos for research purposes
3) Risk to oocyte and embryo donors
4) Possible exploitation of female oocyte donors
5) There is conflict with religious and cultural beliefs
6) There are issues to pertaining to individual informed consent and privacy
7) There are concerns over equity in the use of stem cells for medical treatment
How does induced pluripotent stem cells overcome the ethical implications of the application of stem cells in research and medical applications?
1) Avoids the moral dilemma of destroying a potential human life to save another, as embryos are not destroyed
2) Provides al alternative to the controversial creation of embryos for research and as a source of spare parts
3) Bypasses the risks and medical complications involved in oocyte retrieval
4) Avoids the possible exploitation of female oocyte donors for their oocyte, especially in poorer countries or countries with fewer legal restrictions
Definition of fluid mosaic model
The term ‘mosaic’ means that the proteins are embedding and span in the phospholipid belayer in a random manner
The term ‘fluid’ means that the membrane is in constant motion, the phospholipids, which are held by weak hydrophobic interactions, and proteins are free to move rapidly within the membrane by diffusion
The unsaturated fatty acid of the phospholipids have kinks in them which keeps the molecular from packing together, enhancing fluidity.
What is the role of cholesterol in the cell surface membrane?
Cholesterol acts as a plug which reduce the escape or entry of charged ions and small polar molecules across the cell surface membrane
Cholesterol also increases stability and flexibility of the membrane.
When temperature increases, cholesterol restrains the movement of phospholipids, making the membrane less fluid.
When temperature decreases, cholesterol hinders the close packing of phospholipids, preventing the membrane from ‘freezing’ and making the membrane more fluid.
What are the roles of glycolipids and glycoproteins in the cell surface membrane?
1) Involves in cell-cell recognition, the carbohydrate chain on the protein functions as a marker which distinguishes one cell from another
2) Involves in cell-cell adhesion, binds cell together into tissues
3) Acts as receptor sites for signal molecules such as hormones
Definition of telomeres & the 4 function
Telomeres are nucleoprotein complexes found at both ends of a linear, eukaryotic chromosomes
Telomeres ensure genes are not lost or eroded due to end replication problem with each round of DNA replication, preventing the loss of important genetic information
Telomeres protect and stabilised the terminal ends of chromosomes by preventing the accidental fusion of the single-stranded end of one chromosome to the single-stranded end of another chromosome via complementary base pairing.
Cells with critically short telomeres will undergo apoptosis
Telomeres allow their own extension, by providing an attachment point for telomerase
Definition of a centromere + function
A centromere is a constricted region of a chromosome where two sister chromatids are joined. Spindle fibres attach to centromeres during nuclear division.
Centromeres hold sister chromatids together and ensure proper alignment and segregation of homologous chromosome/ sister chromatids to opposite poles of the cell by being the site where kinetochore assembles and spindle fibres from the centrioles attach.
definition of gene and its structure
A gene refers to a specific sequence of nucleotides in the DNA which codes for a polypeptide or RNA.
A gene consists of both coding and non-coding regions.
Structure of introns + its function
Introns are non-coding DNA sequences that interrupt a gene-coding sequence
Introns are interspersed between exons in a sequence of DNA
Intros enable alternating RNA splicing and the subsequent production of multiple polypeptides from one gene
What is the definition of control elements?
Name 3 and state its structure & function
Control elements are non-coding DNA segments that transcription factors recognise and bind to in order to regulate trancription
1) Promoter
Structure: Promoter is a specific segment of DNA which is usually located upstream of the transcription start site of a gene
Function: Promoter is a recognition site for general transcription factors and RNA polymerase. The promoter recruits RNA polymerase to recognise and bind to the core promoter, forming the transcription initiation complex and initiate transcription at the transcription start site
2) Enhancer
Structure: Enhancers are positive regulatory elements which are usually located futher away from the promoter.
Function: Enhancer is a binding site for activators. The binding of activators to promoters accelerates the formation of transcription initiation complex at the promoter and increases the rate of transcription
3) Silencer
Structure: Silencers are negative regulatory elements which are usually located further upstream of downstream of the promoter of a gene.
Function: Silencer is a binding site for repressors. The binding of repressor to the silencer prevents the assembly of transcription initiation complex at the promoter and decreases or inhibits the rate of transcription.
What is the cell theory?
Cells are the smallest unit of structure in every living thing. The cell is the fundamental unit of structure and function of all living organisms. All known living thing are made up of one or more cells. All cells arise from pre-existing cells by cell division. Cells contain hereditary information which is passed on from cell to cell during cell division.
